1. Field of the Invention
The present invention relates to a liquid discharge head for discharging liquid utilizing thermal energy and a liquid discharge apparatus utilizing such liquid discharge head.
2. Related Background Art
Such liquid discharge head is provided with various mechanisms for achieving stable discharge of liquid (for example ink). As an example, the Japanese Patent Application Laid-Open No. 7-52387 discloses an ink jet recording head equipped with ink temperature controlling function. The configuration of such ink jet recording head is schematically shown in FIG. 9, and FIG. 10 shows the configuration of a temperature control portion formed on a head board of such ink jet recording head.
Referring to FIG. 9, the ink jet recording head is constructed by forming plural heaters Hn on a head board 500, also forming partition walls 501 for forming ink paths corresponding to the heaters Hn, and adjoining a top plate 502 to the partition walls 501 to form discharge opening 503, ink paths 505 and a common liquid chamber 504. The head board 500 is provided thereon, as shown in FIG. 10, a temperature sensor 510 for detecting the head temperature, sub heaters 511a, 511b for regulating the head temperature, and a temperature control circuit for driving the sub heaters 511a, 511b based the output of the temperature sensor 510, composed of an analog converter 512, an amplifier 513, a comparator 514 and a sub heater driver 515.
In the above-described ink jet recording head, the sub heaters 511a, 511b are controlled according to the output of the temperature sensor 510, whereby the head temperature is maintained within a desired temperature range.
For achieving more stable liquid discharge, in addition to the above-described control of the head temperature, there is conceived a method of detecting the state change of the nozzle in detailed manner (by detecting the change in resistance or temperature through the liquid in each nozzle), and controlling the drive of the liquid discharging heater (heat generating member) according to the result of such detection. However, since the sensor for detecting such state change of the nozzle has a relatively high output impedance, the output of such sensor tends to bear noises caused for example by the head driving current. Therefore, if such sensor is provided on the element substrate bearing the heaters, driving circuit, logic devices etc., the detecting precision of the sensor may be deteriorated by the noises caused for example by the heater driving current. In particular, the current (heater driving current) in the head board is increasing because of the recent increase in the number of nozzles in the liquid discharge head and in the driving speed thereof, so that the above-mentioned noise has become an important issue in finely monitoring the state change of the nozzles.
Also there is recently developed a head in which the element substrate and the top plate are formed with a same silicon material in order to avoid displacement therebetween resulting from the thermal expansion induced by the driving of the heat generating members, and such configuration has enabled to suitably distribute the sensor and various circuit elements on such element substrate and top plate according to the functions of such elements, but the head in consideration of the above-mentioned noise issue has never been developed and has been longed for.
Further, the output signal from the sensor can be relieved from the influence of the noises by amplification with an amplifier, but such noises tend to be picked up if the distance between the sensor and the amplifier increases. It is therefore important to take the noise issue into consideration also in determining the positional relationship of the sensor and the amplifier.
In consideration of the foregoing, the object of the present invention is to provide a liquid discharge head capable of more stable liquid discharge and a liquid discharge apparatus provided with such liquid discharge head.
The above-mentioned object can be attained, according to the present invention, by a liquid discharge head comprising first and second substrates which are mutually adjoined to constitute plural discharge apertures and plural liquid paths respectively communicating therewith, wherein the first substrate bears energy conversion elements, for converting electrical energy into energy for discharging the liquid in the liquid paths, respectively in the liquid paths while the second substrate bears detection elements, for detecting a liquid state in the liquid paths, respectively in the liquid paths and amplifier means for amplifying the respective outputs of the detection elements.
Also according to the present invention, there is provided a liquid discharge apparatus featured by comprising the above-mentioned liquid discharge head and driving the energy generating elements of the first substrate constituting the liquid discharge head under adjustment based on the result of detection by the detection elements of the second substrate constituting the liquid discharge head, thereby discharging liquid onto a recording medium to form a record thereon.
According to the present invention, as explained in the foregoing since the detection elements and the amplifier means are provided on the second substrate which is different from the first substrate bearing the energy conversion elements, the outputs of the detection elements are less contaminated by the noise (of the heater driving current) generated in driving the energy conversion elements and the distance between the detection element and the amplifier means can be made shorter, so that the precision of detection is not deteriorated.
Also according to the present invention, the detection elements and the amplifier means are formed on the second substrate which is more spacious in comparison with the first substrate bearing the energy conversion elements, so that the aforementioned issue of limitation in space is not encountered.
Furthermore, in a liquid discharge head provided with switching means for switching the locations of detection, the detection elements are serially driven so that the space for positioning such detection elements on the second substrate can be limited.
According to the present invention, there is also provided a liquid discharge head comprising first and second substrates which are to be mutually adjoined to form plural discharge apertures and plural liquid paths respectively communicating with the discharge apertures, wherein the first substrate is provided with energy conversion elements, for converting electrical energy into energy for discharging the liquid in the liquid paths, respectively corresponding to the liquid paths, and the second substrate is provided with detection elements for detecting the state of the liquid in the liquid paths respectively corresponding to the liquid paths and amplification means for amplifying the respective outputs of the detection elements.
According to the present invention, there is also provided a method for producing a liquid discharge head including plural discharge apertures for discharging liquid; first and second substrates which are to be mutually adjoined to form plural liquid paths respectively communicating with the discharge apertures; plural energy conversion elements respectively provided in the liquid paths, for converting electrical energy into energy for discharging the liquid in the liquid paths; and plural elements or electrical circuits of different functions for controlling the drive condition of the energy conversion elements, the elements or electrical circuits being dividedly provided on the first and second substrates according to the functions, the method comprising:
a step of forming plural protruding electrical connecting portions, on either of the first and second substrates, for mutually and electrically connecting the elements or electrical circuits of the first and second substrates;
a step of forming plural recessed electrical connecting portions, on the other of the first and second substrates, for respectively engaging with the protruding electrical connecting portions and being electrically connected therewith; and
a step of engaging the plural protruding electrical connecting portions with the respectively corresponding plural recessed electrical connecting portions at the adjoining of the first and second substrate.
According to the present invention, there is also provided a method for producing a liquid discharge head including plural discharge apertures for discharging liquid; first and second substrates which are to be mutually adjoined to form plural liquid paths respectively communicating with the discharge apertures; plural energy conversion elements respectively provided in the liquid paths, for converting electrical energy into energy for discharging the liquid in the liquid paths; and plural elements or electrical circuits of different functions for controlling the drive condition of the energy conversion elements, the elements or electrical circuits being dividedly provided on the first and second substrates according to the functions, the method comprising:
a step of preparing a first silicon wafer including plural first substrates, each provided with a first electrical connecting portion for mutually and electrically connecting the elements or electrical circuits of the first and second substrates;
a step of preparing a second silicon wafer including plural second substrates, each provided with a second electrical connecting portion for mutually and electrically connecting the elements or electrical circuits of the first and second substrates;
an impingement step of impinging the first silicon wafer on the second silicon wafer in such a manner that the first electrical connecting portion is opposed to the second electrical connecting portion corresponding to the first electrical connecting portion;
an adjoining step of adjoining the first electrical connecting portion with the second electrical connecting portion corresponding to the first electrical connecting portion by eutectic bonding; and
a cutting step of integrally cutting the adjoined first and second silicon wafers after the adjoining step.
In the present specification, the word xe2x80x9cupstreamxe2x80x9d or xe2x80x9cdownstreamxe2x80x9d defines a position with respect to the direction of liquid flow from a liquid supply source to a discharge aperture through a bubble generating area (or a movable member) or with respect to the direction in such configuration.